Select / sub select? query... help...

Hello -

  I'm trying to figure out how to write a particular query and need some
assistance.  I imagine this is extremely simple.  I have the table defined
below with five records.  This table keeps track of peoples names.  Each
person has a unique ID number ("person_id").  The table can also keep track
of alias names for these people.  Each record has a flag ("isalias")
indicating whether or not this record indicates a persons real name or a
persons alias name.  If it is an alias name then an additional field
("alias") has the number indicating this persons real name record by
person_id  (ie alias field of an alias record == the person_id of the real
name record).

  I want a query that will select all entries where "isalias" is true and
will display the person_id, first, and last fields from the alias record and
ALSO the first and last fields from the real name entry.

Output would be something like this for the example data below

3 - Johns - Alias - John - Smith
4 - Marks - Alias - Mark - Twain


Any thoughts on how this can be accomplished easily / efficiently?

Thanks
-Jim


             Table "public.people"
  Column   |         Type          | Modifiers
-----------+-----------------------+-----------
 person_id | integer               |
 first     | character varying(20) |
 last      | character varying(20) |
 alias     | integer               |
 isalias   | boolean               |

Containing the example data:

 person_id | first | last  | alias | isalias
-----------+-------+-------+-------+---------
         1 | John  | Smith |     0 | f
         2 | Mark  | Twain |     0 | f
         3 | Johns | Alias |     1 | t
         4 | Marks| Alias |     2 | t
         5 | someone | else |   0| f

(5 rows)